1. Field of the Invention
The present invention relates to the use of lens ducts to deliver pump light to laser gain materials, and more specifically, it relates to means for delivering pump light to a laser gain element while maintaining access for a laser or probe beam.
2. Description of Related Art
The design of solid-state lasers is greatly determined by the architecture for pump light delivery and similarly, the brightness (W/cm2-steradian) of pump light. For instance, some devices utilize pump light impinging on a face of a slab or along the barrel of a rod in a geometry commonly referred to as side-pumping. However, in some cases, it is desirable to utilize an end-pumping geometry in order to achieve high delivery efficiency, or due to limitations in the absorption length due to dopant concentration.
Because of limitations in diode array brightness, it is often desirable to confine the pump light in the gain element via total internal reflection (TIR), since the Rayleigh range may be much less than the absorption length. The limited diode brightness also places limitations on access to the laser beam if the pump light fills the entire cross-sectional area of the gain element. One geometry for diode-array end-pumping uses a dichroic coating on one endface of the laser gain element to achieve high reflectivity at the laser wavelength and high transmission for the pump wavelength over its angular distribution. This allows the pump light to be delivered through this endface while the laser beam is reflected off of the same face and extracted from the laser medium through another face, usually the other endface. However, the use of the dichroic coating places restrictions on how close the pump and laser wavelengths can be, as well as the angular distribution of the pump light. In addition, there are situations where pump light enters the gain element through a surface and it would be desirable to access the laser beam through the same surface, for instance to pump both ends of a slab or rod.